pointzip: Compressing PTS and PTX files as LAZ

Martin Isenburg

overview:
The pointzip.exe program can efficiently
convert large 3D scans from the PTS or PTX format (produced by Leica's Cyclone and
other point cloud software) into the compressed LAZ or the uncompressed LAS format.
The corresponding pointUNzip.exe program can
convert the compressed LAZ or the uncompressed LAS files back to the original PTS
or PTX files.

When using the compressed LAZ format (which uses the LASzip compression algorithm) the reduction in file size is a factor
of 5 to 15 depending on the coherency in the point order and the number of digits stored. The user has full control
about the level of precision. The intensity
range of -2048 to 2047 in the PTS format gets mapped to 0 4095 during compression to LAZ
or LAS and back to -2048 to 2047 during decompression to PTS. Similarly, the intensity
range of 0.0 to 1.0 in the PTX format gets mapped to 0 4095 in LAZ/LAS and back. This
makes compression not only lossless but also produces valid and compatible LAZ or LAS
files that can be imported into other software packages.

"Works well on larger files as well. I was able to compress a 46 GB PTS file to 3.5 GB LAZ @ mm accuracy in 73 minutes."

"I zipped a 3.71GB PTS file using xyziRGB parsing and mm precision. My PTS file was from a HDS7000 merged with color photography. The output file was 303MB LAZ in 5 minutes. That's a great compression rate!"